Compartmentalized mast cell degranulations in the ovarian hilum, fat pad, bursa and blood vessel regions of the cyclic hamster: Relationships to ovarian histamine and blood flow

Abstract

Ovaries from hamsters on each day of the oestrous cycle at 09.00 h were observed for the number of mast cells, the pattern of mast cell degranulation. histamine concentration and blood flow. On day 4 (pro-oestrus), ovaries were also observed at 9.00, 15.00and21.00 h. Mast cell degranulation was evaluated by 3 criteria: (1) no degranulation = less than 5 granules dispersed from the cell; (2) moderate degranulation = 5 or more granules dispersed but less than 15, and (3) extensive degranulation = 15 or more granules released. Blood flow was determined using radio-active microspheres in anaesthetized animals. Mast cells were observed in fat pad (beyond 2 mm of the bursal mesothelium). bursal (within 2 mm of the bursal mesothelium). hilum and near ovarian blood vessels (these 4 regions are collectively called the ovarian complex). The distribution of ovarian mast cells was not uniform. Most mast cells were near ovarian blood vessels (42.2%) and in the fat pad (37.2%). A moderate number of eel Is were in the bursal wall (20%) and only a few cells were observed in the hilum (0.64%). Mast cell number remained unchanged on days 1-4 of the cycle in each ovarian compartment. However, summation of the number of mast cells m the entire ovarian complex revealed a significant decline in number at 15.00 hon pro-oes-trus. Alterations in mast cell degranulation were primarily restricted to 2 periods of the cycle (pro-oestrus and di-oes-trus). An increase in moderate hut not extensive degranulation was observed in only the fat pad and bursa on day 2 when compared with day I values. In most ovarian compartments on pro-oestrus, degranulation was higher than on any other day of the cycle. At 15.00 h on pro-oestrus, extensive degranulation in bursa. fat pad and blood vessel regions (but not hilum) coincided with an increase in ovarian histamine and decline in number of mast cells; ovarian blood flow also increased at that time but remained unchanged the remainder of the cycle. The results indicate that significant mast cell degranulation could occur on days other than pro-oestrus, although on pro-oestrus mast cell degranulation was increased, that not all ovarian compartments exhibit the same pattern of mast cell degranulation and that changes in ovarian blood may correlate with increased histamine and mast cell degranulation on pro-oestrus but not necessarily on other days of the cycle. © 1991 S. Karger AG, Basel.